This invention relates to the discovery of a new gene, vatE, encoding an acetyltransferase inactivating streptogramin A, which is widely distributed in virginiamycin-resistant enterococcus faecium strains.
Streptogramin, virginiamycin, pristinamycin, and synergistin are produced by streptomyces, and consist of synergistic mixtures of two chemically different molecules: A and B compounds (10) In some European countries and in Algeria, these mixtures are used both orally and topically, mostly against staphylococcal infections. Virginiamycin is used as growth promoter in animal feed in Europe and in the U.S.A. Virginiamycin-resistant Enterococcus faecium are prevalent in fecal and intestinal samples from turkeys, pigs, broilers, and farmers in Europe and America (1, 14, 19, 20). Since bacteria can be transferred via food from animals to humans, this is alarming, in particular because quinupristin/dalfopristin (J. Antimicrob. Agents Chemother., 1992, 30[suppl.30]), an injectable mixture of semi-synthetic streptogramins soon to be commercialized (Synercid), is expected to be widely used, mainly to treat vancomycin-resistant E. faecium infections.
The satA gene (18) encoding an acetyltransferase inactivating A compounds was isolated from an E. faecium plasmid. It was found in only 29% of the 140 tested E. faecium strains isolated in Dutch and Danish farms and resistant to the mixtures (13, 14). Five of the E. faecium strains isolated in Denmark harbored a large plasmid conferring resistance to the mixture and which was transferable by filter mating experiments to an E. faecium recipient (14). None of the transconjugants harboring these plasmids carried satA, vat, vatB, vga, or vgaB (14). These results suggested that the E. faecium strains contained other unidentified streptogramin A resistance gene(s). Thus, there continues to exist a need in the art for the identification of new genes specific for Enterococcus faecium resistant to streptogramin A and related compounds.